Structural snapshots of concerted double E–H bond activation at a transition metal centre

Abstract

Bond activation at a transition metal centre is a key fundamental step in numerous chemical transformations. The oxidative addition of element-hydrogen bonds, for example, represents a critical step in a range of widely applied catalytic processes. Despite this, experimental studies defining steps along the bond activation pathway are very rare. In this work, we report on fundamental studies defining a new oxidative activation pathway: combined experimental and computational approaches yield structural snapshots of the simultaneous activation of both bonds of a β-diketiminate-stabilized GaH unit at a single metal centre. Systematic variation of the supporting phosphine ligands and single crystal X-ray/neutron diffraction are exploited in tandem to allow structural visualization of the activation process, from a η-H,H σ-complex showing little Ga-H bond activation, through species of intermediate geometry featuring stretched Ga-H and compressed M-H/M-Ga bonds, to a fully activated metal dihydride featuring a neutral (carbene-type) N-heterocyclic Ga ligand.

Coordination and Activation of EH Bonds (E=B, Al, Ga) at Transition Metal Centers

“…56 Mechanistically, the fundamental processes implicit in EdH bond activation have also begun to be illuminated, with studies of the interaction of {HC(MeCDippN) 2 }GaH 2 with cationic rhodium bis(phosphine) fragments, [(R 3 P) 2 Rh] + , for example, showing that the degree of GadH bond activation can be "tuned" by variation in the phosphine ligands, to provide snapshots of the activation process leading to gallium-to-rhodium transfer of the two hydrogen atoms. 57 …”

Stabilized Gallylene in a Pincer‐Type Ligand: Synthesis, Structure, and Reactivity of PGaIP‐Ir Complexes

“…[12] A quantum theory of atoms in molecules (QTAIM) analysis showed the bond critical point (bcp) for the IrÀCl2 bond, but not between Ga and Cl2. [15] Such ac omplexationinduced reduction of trivalent Group 13 metals to metallylenes with neutral, late transition metals are rather rare, [16] whereas reactions with highly reactive,d ianionic carbonyl metalates such as K 2 [Fe(CO) 4 ]w ith the Group 13 chlorides were well developed to give XL n Ga I ÀFe(CO) 4 complexes via double salt exchange. TheX -ray structural analysis demonstrated the added chloride bonds to Ir,n ot to Ga, to form the octahedral iridium trichloride complex bearing aG aCl as as upporting ligand (Figure 2b).…”

Stabilized Gallylene in a Pincer‐Type Ligand: Synthesis, Structure, and Reactivity of PGaIP‐Ir Complexes

“…[14] Notably,t he IrÀCl2 bond of 4 is elongated (2.5459(9) )c ompared with that in the related pincer-type Ir III Cl complexes,s uggesting the strong trans influence of the Ga I metalloligand. [15] Such ac omplexationinduced reduction of trivalent Group 13 metals to metallylenes with neutral, late transition metals are rather rare, [16] whereas reactions with highly reactive,d ianionic carbonyl metalates such as K 2 [Fe(CO) 4 ]w ith the Group 13 chlorides were well developed to give XL n Ga I ÀFe(CO) 4 complexes via double salt exchange. [17] This is the first example of synthesis and structural analysis of gallylene-based pincer complexes and could be au seful method to access av ariety of metallylene-coordinated late transition-metal complexes.…”